The present invention relates to an optical connection for an integrated electronic circuit and is in particular, applied to interconnections of such circuits.
The need for increasingly higher rates for operating integrated electronic circuits leads to increasingly higher integration of these circuits. This integration finds its limits in the unavoidable increase in the size of the circuits, which leads to an increase in cost of the latter (because of a reduction of the manufacturing cost-effectiveness). A compromise then imposes interconnections of integrated electronic circuits of reasonable size.
It is known how to connect two integrated electronic circuits to each other via electrical links. However, with the increase in operating rates of the circuits (clock frequencies above 500 MHz), electromagnetic coupling phenomena occur between parallel electrical conductors, couplings which induce a deterioration of the signal/noise ratio and risks of malfunction.
It is also known how to use optical links instead of electrical conductors, these optical links providing better separation between transmission channels.
Such optical links comprise light transmitters and receivers as well as link channels.
The link channels may use holograms or slightly confined overhead bundles or even optical fibers. The light transmitters and receivers are mounted on integrated electronic circuits which are to be interconnected and are electrically connected to these circuits. It is specified that the transmitters are generally vertical cavity surface emission lasers (VCSEL) which only occupy a small surface on the substrates on which they are mounted and have a low threshold current.
FIG. 1 schematically illustrates an known interconnection between two integrated electronic circuits 2 and 4. An optoelectronic component 6 is electrically connected to the integrated circuit 2 via microbeads of solder 8. Another optoelectronic component 10 is electrically connected to the integrated circuit 4 via microbeads of solder 12.
An optical circuit 14 formed on a substrate 15 and comprising an optical waveguide 16 is provided for optically connecting the optoelectronic components 6 and 10 to each other.
Component 6 is for example a light transmitter whereas component 10 is a light receiver.
Electrical signals transmitted by the circuit 2 are then converted into light signals by component 6. These light signals propagate in the optical waveguide 16 and are detected by component 10 which reconverts these light signals into electrical signals. The integrated circuit 4 receives the latter. So, an interconnection is actually available between circuits 2 and 4.
However, optical interconnections between integrated electronic circuits of the interconnection type of FIG. 1 have a drawback: these interconnections require great accuracy for xe2x80x9caligningxe2x80x9d, i.e., optically coupling, optical link channels with light transmitters and receivers. For example, in the case of FIG. 1, great accuracy is required for optical coupling between the optical waveguide 14 and component 6 or even component 10.
The object of the present invention is to overcome the above drawback by providing an interconnection of integrated electronic circuits which is easier to produce than known interconnections, as mentioned above, as it requires alignments with less accuracy.
More generally, the present invention relates to an optical connection for an integrated electronic circuit, the making of which uses coupling of an electronic type, coupling which requires less accuracy than optical coupling.
Specifically, the object of the present invention is an optical connection for an integrated electronic circuit, this optical connection being characterized in that it comprises an optical circuit formed on a substrate and comprising an optical waveguide and an optoelectronic component which is optically coupled to the optical waveguide and has at least either of the two electronic-optical converter and optoelectronic converter functions, and in that the optical circuit is connected to the integrated electronic circuit via a purely electrical link between the optoelectronic component and the integrated electronic circuit in order to convert the electrical signals transmitted by the integrated electronic circuit into optical signals which then propagate in the optical waveguide and/or to convert such optical signals into electrical signals which are then received by the integrated electronic circuit.
The object of the present invention is also an optical connection between first and second integrated electronic circuits, this optical connection being characterized in that it comprises an optical circuit formed on a substrate and comprising an optical waveguide and first and second optoelectronic components which are optically coupled with the optical waveguide, the first optoelectronic component having at least either of the two electronic-optical converter and optoelectronic converter functions, and the second optoelectronic component having at least either of the two optoelectronic and electronic/optical converter functions and in that the optical circuit is connected to the first and second integrated electronic circuits via purely electrical links between the first and second optoelectronic components and the first and second integrated electronic circuits respectively so that electrical signals transmitted by the first and/or second integrated electronic circuits are converted into optical signals which then propagate in the optical waveguide and are then reconverted into electronic signals, the latter being then received by the second and/or first integrated electronic circuit.
In the invention, each electronic-optical converter is a laser comprising a resonant cavity delimited by two mirrors which are formed on the optical waveguide and an amplifying medium placed in a recess formed across this optical waveguide between both mirrors.
First and second integrated electronic circuits may be formed on different substrates or conversely on the same substrate, respectively.
Preferably, the optical circuit and each integrated electronic circuit are made from materials substantially having the same thermal expansion coefficient.
Each purely electrical link may be made by means of microbeads of a fusible material.
Both mirrors may be Bragg gratings which are photo-engraved or etched on the optical waveguide.
Alternatively, each mirror may be a slot which crosses the optical waveguide.
Preferably, the space between the amplifying medium and the whole of the recess contains an optical index adapter, a fluid or a gel for example.